Anglo-Saxon
Anglo-Saxon or Old English is the ancestor of Modern English. It is a West Germanic Language and like Dutch and Low Saxon (Low German) it did not go through the High German Consonant Shift.
The People
The Saxons were invited to Britain to help fight off the Picts. A large migration of Saxons then moved from modern Northern Germany and Holland to England. The next few centuries they expanded westward constantly and gained more land. The people then became mixed with the Romano-British people already living there.
In the 9th and 10th centuries, Danish Vikings invaded parts of England. The Old Norse influence can still be seen today.
Orthography
Runic
Early forms of Anglo-Saxon writing was in Runic. It was an expansion of the original 24 rune Fuþark, and had become Fuþorc. Because the language had shifted to include new sounds, the alphabet itself shifted and included several new letters that had not been in the Elder Fuþark. However they did not develop the one Staff system similar to the runic designs in Norway, Sweden and Denmark.
When the Latin Alphabet was introduced, Anglo-Saxon added two symbols to the Latin alphabet from Runic, those would be "þ" /θ/ and "ƿ" /w/ from runic, called Thorn and Wynn respectively.
Alphabetic
The Old English Alphabet was a Latin based alphabet and included a few extra symbols that modern English speakers would not necessarily recognize. The diagraphs were also quite different than modern spelling and included cg /ʤ/ and c /ʧ/ and sc /ʃ/.